Electronic device and method for manufacturing the same

ABSTRACT

An electronic device is provided using wiring comprising aluminum to prevent hillock or whisker from generating, wherein the wiring contains oxygen atoms at a concentration of 8×10 18  atoms·cm −3  or less, carbon atoms at a concentration of 5×10 18  atoms·cm −3  or less, and nitrogen atoms at a concentration of 7×10 17  atoms·cm −3  or less; furthermore, a silicon nitride film is formed on the aluminum gate, and an anodic oxide film is formed on the side planes thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S.application Ser. No. 09/302,679, filed on Apr. 30, 1999, which is adivisional of U.S. application Ser. No. 08/895,432, filed Jul. 16, 1997,now U.S. Pat. No. 5,929,527.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electronic device whose electrodesand wiring are constructed by aluminum or a material containing aluminumas the principal component. It also relates to a method formanufacturing the same.

2. Description of the Related Art

Recently, active-matrix liquid crystal devices equipped with large-areaimage planes are attracting much attention. Such active-matrix liquidcrystal devices not only require image planes having larger area, butalso demand for finer patterning.

The use of a material having low electric resistance for the wiringmaterial is necessary to fulfill the demand above, because the delay ofsignal propagating on wiring becomes a problem in a device with a sizeof 10×10 inch² or larger.

Concerning a wiring material having low electric resistance, aluminum isthe most desirable one. However, aluminum brings about the problem ofheat resistance on its use in the manufacturing method (refer to areview paper in Display and Imaging, 4 (1996), pp. 199-206; published byScience Communications International).

More specifically, in the steps such as the formation of various typesof thin films by deposition and the annealing of the resulting films, orin the irradiation of laser light and the implantation of impurity ions,aluminum undergoes problematic abnormal growth so as to form protrusionscalled hillock or whisker. These hillock and whisker are believed to beattributable to the poor heat resistance of aluminum.

Those protrusions known as hillock or whisker sometimes grow as long as1 μm or even longer. This phenomenon leads to the occurrence of shortcircuit between wirings.

The problem above can be prevented from occurring by forming an anodicoxide film on the surface of the aluminum wiring (see the referenceabove).

According to the study of the present inventors, it is found that theanodic oxide film (assumably containing Al₂O₃ as the principalcomponent) is robust and is effective for preventing hillock or whiskerfrom generating. On the other hand, however, such a robust materialmakes it difficult to form contact holes on the aluminum wiring.

SUMMARY OF THE INVENTION

In the light of the aforementioned circumstances, an object of thepresent invention is to overcome the problem of heat resistance of analuminum wiring, and to provide a technique which solves the difficultyin forming contact holes on the aluminum wiring having an anodic oxidefilm formed thereon.

According to one constitution of the present invention, there isprovided an electronic device characterized in that it comprises a filmpattern made of aluminum or a material containing aluminum as theprincipal component thereof, wherein the film made of aluminum or amaterial containing aluminum as the principal component contains oxygenatoms at a concentration of 8×10¹⁸ atoms·cm⁻³ or less, carbon atoms at aconcentration of 5×10¹⁸ atoms·cm⁻³ or less, and nitrogen atoms at aconcentration of 7×10¹⁷ atoms·cm⁻³ or less.

By employing the constitution above, the maximum height of the generatedprotrusions such as hillock and whisker can be suppressed to 500 Å orless.

According to another constitution of the present invention, there isprovided a method for manufacturing an electronic device comprising afilm pattern made of aluminum or a material containing aluminum as theprincipal component thereof, wherein the film made of aluminum or amaterial containing aluminum as the principal component contains oxygenatoms at a concentration of 8×10¹⁸ atoms·cm⁻³ or less, carbon atoms at aconcentration of 5×10¹⁸ atoms·cm⁻³ or less, and nitrogen atoms at aconcentration of 7×10¹⁷ atoms·cm⁻³ or less; and the film pattern issubjected to a process whose process temperature is 400° C. or lower.

By controlling the process temperature to 400° C. or lower, it ispossible to make the best of the effect of controlling the concentrationof oxygen, carbon, and nitrogen atoms to a desired low level.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1C are diagrams showing the steps of manufacturing a thinfilm transistor;

FIGS. 2A to 2C are diagrams showing the steps of manufacturing a thinfilm transistor;

FIGS. 3A and 3B are diagrams showing the steps of manufacturing a thinfilm transistor;

FIGS. 4A to 4C are diagrams showing the steps of manufacturing anotherthin film transistor;

FIGS. 5A to 5C are diagrams showing the steps of manufacturing anotherthin film transistor;

FIGS. 6A to 6D are diagrams showing the steps of manufacturing a stillother thin film transistor;

FIGS. 7A and 7B are diagrams showing the steps of manufacturing a stillother thin film transistor;

FIG. 8 is a schematic of a film deposition apparatus; and

FIGS. 9A to 9E schematically show devices utilizing liquid crystalpanels.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1B, an embodiment of the present invention comprisesforming a silicon nitride film 107 on the upper plane of a patternedaluminum film 106 containing 8×10¹⁸ atoms·cm⁻³ or less of oxygen atoms,5×10¹⁸ atoms·cm⁻³ or less of carbon atoms, and 7×10¹⁷ atoms·cm⁻³ or lessof nitrogen atoms, and also forming anodic oxide films (oxide films) 108and 109 on the side planes of the patterned aluminum film 106.

By utilizing the constitution above, the formation of protrusions suchas hillock and whisker can be suppressed, and contacts can be formedmore easily.

The present invention is described in detail referring to the preferredembodiments according to the present invention. It should be understood,however, that the present invention is not to be construed as beinglimited to the examples below.

EXAMPLE 1

FIGS. 1A to 1C schematically show the fabrication process (crosssection) of the present example. The present example refers to afabrication process of a thin film transistor provided to the pixelmatrix portion of an active matrix-type liquid crystal display(generally known as “pixel transistor”).

Referring to FIG. 1A, a base film (not shown) is formed on the surfaceof a glass substrate 101. As the base film (not shown) for use in thepresent example, a 3,000-Å-thick silicon oxide film is formed bysputtering.

The base film functions to relax the influence of the impuritiesdiffused from the glass substrate and of the minute irregularities onthe surface of the glass substrate. Although a glass substrate is usedin this example, a quartz substrate can be used in the place thereof.

After forming the base film on the glass substrate 101, a 500-Å-thickamorphous silicon film (not shown), which is the starting film for asemiconductor film that constitutes the active layer 102 of the thinfilm transistor, is formed by means of plasma CVD.

The resulting amorphous silicon film is subjected to laser irradiationto obtain a crystalline silicon film (not shown). The crystallinesilicon film is patterned to form an active layer pattern 102.

Then, a 1,000-Å-thick silicon oxide film 103 which functions as a gateinsulating film is formed by means of plasma CVD.

Once the silicon oxide film 103 is obtained, an aluminum film 104 isformed at a thickness of 4,000 Å by sputterin. A silicon nitride film105 is on the aluminum film 104. Thus is obtained a state as is shown inFIG. 1A.

In the present example, scandium is added into the aluminum film at aconcentration of 0.18% by weight.

The addition of scandium suppresses the generation of hillock andwhisker in the later steps. Scandium is effective for the preventinghillock and whisker from generating, because it suppresses abnormalgrowth of aluminum.

Then, a patterned aluminum denoted by a reference numeral 106 isobtained by patterning a layered film of aluminum film 104 and siliconnitride film 105. A silicon nitride film denoted by a reference numeral107 remains on the gate electrode 106. That is, the patterned aluminum106 becomes the gate electrode. A gate line is extended from the gateelectrode 106.

In the pixel matrix portion, the gate lines extended from the gateelectrodes 106 are arranged in a lattice together with source lines toform a matrix.

Anodic oxidation using the gate electrode 106 as the anode is performedthereafter to form anodic oxide films 108 and 109 on the thus exposedside planes of the aluminum film. The anodic oxide film are eachprovided at a thickness of 500 Å.

In the anodic oxide step above, an ethylene glycol solution containing3% of tartaric acid, which is neutralized by ammonia water, is used asthe electrolytic solution. Thus, an anodic oxide film can be formed byapplying electric current to platinum as a cathode and the aluminum filmas an anode placed in the electrolytic solution.

The anodic oxide film 108, 109 thus obtained is dense and robust. Thefilm thickness of the film obtained in the anodic oxidation step can becontrolled by adjusting the applied voltage.

In the step above, an anodic oxide film is not formed on the upper planeof the gate electrode 106, because the electrolytic solution is broughtinto contact with only the side planes of the gate electrode 106. Thusis obtained a structure as is shown in FIG. 1B.

A source region 110, a channel region 111, and a drain region 112 areformed thereafter by introducing phosphorus (P) by doping. Plasma dopingis used in the present example as a means of doping. A structure shownin FIG. 1C is thus obtained.

Doping of P is performed in this case to fabricate an N-channel typethin film transistor. However, doping of boron (B) must be carried outto fabricate a P-channel type thin film transistor.

The doping step produces such a condition as heating of the sample orinevitable heating of the sample. However, from the viewpoint of theheat resistance of aluminum, it is important to maintain the sample at atemperature of 400° C. or lower. Care should be taken if the heatingtemperature exceeds 400° C., because the generation of hillock (orwhisker; these are not clearly distinguished from each other) becomesapparent.

Upon completion of the doping step, laser light is irradiated to theresulting structure to activate the dopant and the doped regionsimultaneously.

A 2,000-Å-thick silicon nitride film 113 is formed thereafter by meansof plasma CVD to provide a first interlayer insulating film (FIG. 2A).

A polyimide film 114 is formed thereafter by means of spin coating toprovide a second interlayer insulating film. A planar surface can beobtained by using polyimide for the interlayer insulating film.

Contact holes 115 and 116 for the source and drain regions are formedthereafter. Thus is obtained a structure as is shown in FIG. 2A.

Then, a layered film consisting of titanium film, aluminum film, andtitanium film in this order is formed by sputtering, and is patterned toobtain a source electrode 117 and a drain electrode 118. Thus isobtained a structure as is shown in FIG. 2B.

A third interlayer insulating film 119 is formed by using polyimide.After forming a contact hole to the drain electrode 118 thereafter, anITO pixel electrode 120 is formed. The resulting structure is shown inFIG. 2C.

Thus, a complete thin film transistor is implemented by performing heattreatment under gaseous hydrogen to compensate for the defects that arepresent inside the active layer.

EXAMPLE 2

The present example refers to a process to be carried out simultaneouslywith the fabrication process described in Example 1; more specifically,it relates to a process for manufacturing a thin film transistor to beequipped in a peripheral drive circuit that is formed in the peripheryof the pixel matrix portion. The present example again describes aprocess for manufacturing an N-channel type thin film transistor.

The steps in manufacturing the thin film transistor according to thepresent example are the same as those described in Example 1 withreference to FIGS. 1A to 1C (as a matter of course, there are somedifferences concerning the wiring pattern and the size of the activelayer pattern).

First, a structure with reference to FIG. 1C is obtained by followingthe steps described in Example 1. Then, referring to FIG. 3A, a siliconnitride film 113 is formed as a first interlayer insulating film.

A polyimide layer 114 is formed as a second interlayer insulating film.Contact holes 301, 302, and 303 are formed thereafter.

Because there is not anodic oxide film but a silicon nitride film formedon the upper plane of the gate electrode 106, the contact hole 302 canbe formed easily thereon.

In the constitution according to the present example, contact holes 301,302, and 303 are formed at the same time by using dry etching. Thus isobtained a structure as is shown in FIG. 3A.

A three-layered film consisting of titanium film, aluminum film, andtitanium film is formed by sputtering. A source electrode 304, a gatelead electrode 305, and a drain electrode 306 are formed by patterningthe resulting three-layered film. The structure shown in FIG. 3B isobtained in this manner.

Then, a hydrogenation step similar to that described in Example 1 isperformed to complete a thin film transistor.

Steps for manufacturing an N-channel type thin film transistor aredescribed in the description above. In general, an N-channel type thinfilm transistor and a P-channel type thin film transistor disposed in acomplementary arrangement are used for a peripheral drive circuit.

EXAMPLE 3

The present example refers to a process for manufacturing a thin filmtransistor comprising a low concentration impurity region interposedbetween a channel region and a drain region.

FIGS. 4A to 4C and FIGS. 5A to 5C show the steps for manufacturing athin film transistor according to the present example. First, a basefilm (not shown) is formed on the surface of a glass substrate 401.Then, an amorphous silicon film is formed, and is crystallized byirradiating a laser radiation. Thus is obtained a crystalline siliconfilm. The resulting crystalline silicon film is patterned to form anactive layer 402 for the thin film transistor.

Then, a silicon oxide film 403 which functions as a gate insulating filmis formed, and an aluminum film 404 is formed thereafter.

A silicon nitride film 405 is formed on the aluminum film. Thus isobtained a structure shown in FIG. 4A.

An aluminum pattern 406 is obtained by applying patterning to thestructure with reference to FIG. 4A. The resulting aluminum pattern isthe base pattern of the gate electrode that is to be formed later. Aremaining silicon nitride pattern is also shown by a reference numeral407. Thus is obtained a structure as is shown in FIG. 4B.

Anodic oxidation is performed thereafter to form anodic oxide films 409and 410 by using the aluminum pattern 406 as the anode.

In the present example, an aqueous 3% oxalic acid solution is used asthe electrolytic solution. The anodic oxide film formed in this step isporous, and can be grown to a growth length of several micrometers. Thegrowth length can be controlled by adjusting the duration of anodicoxidation. Thus is obtained a structure as is shown in FIG. 4C, in whichthe pattern 408 becomes the gate electrode.

Then, anodic oxidation is performed again. In this case, anodicoxidation is performed under the same conditions as those employed informing dense anodic oxide films in Example 1. Thus are obtained denseanodic oxide films 411 and 412 as shown in FIG. 5A.

The dense anodic oxide films 411 and 412 are formed at a thickness of500 Å. The dense anodic oxide films are formed selectively on the sideplanes of the gate electrode 408, because a silicon nitride film 407 isformed previously on the upper plane of the gate electrode 408.Furthermore, because the electrolytic solution permeates the porousanodic oxide films 409 and 410, dense anodic oxide films 411 and 412 areformed as shown in FIG. 5A.

Phosphorus (P) atoms are implanted thereafter by employing plasma dopingin the present example. Thus are formed a source region 413, an I-typeregion 414, and a drain region 415 in a self-aligned manner as is shownin FIG. 5B.

Then, the porous anodic oxide films 409 and 410 are removed selectively.Referring to FIG. 5C, a part of the silicon nitride film 407 on theupper portion of the anodic oxide films 409 and 410 is removed togetherwith the anodic oxide films.

Subsequently, doping of P atoms is performed again. In the present step,the doping is carried out at a dose lower than that employed in theprevious doping step. In the present step, low concentration impurityregions 416 and 418 are formed in a self-aligned manner, and a channelforming region 417 is also formed in a self-aligned manner.

The low concentration impurity regions 416 and 418 contain phosphorus(P) at a concentration lower than that for the source region 413 or thedrain region 415.

In general, the low concentration impurity region 418 on the drainregion side is called as “LDD (lightly doped drain) region”.

Once a structure as shown in FIG. 5C is obtained, laser light isirradiated to thereby anneal the region subjected to doping.

In the constitution described in the present example, the upper plane ofthe gate electrode (and the gate line extending therefrom) is covered bya silicon nitride film, and the side plane thereof is covered by a denseanodic oxide film. By employing such a constitution, the generation ofhillock or whisker on the surface of the gate electrode can besuppressed during the steps of doping impurity and irradiating laserradiation. Moreover, in such a structure, contacts to gate electrodes(or gate lines) can be formed more easily.

EXAMPLE 4

The present example refers to a thin film transistor of a so-calledbottom-gate type constitution, in which the gate electrode is providedbetween the active layer and the substrate.

FIGS. 6A to 6D and FIGS. 7A and 7B show the steps for manufacturing athin film transistor according to the present example. First, a3,000-Å-thick aluminum film 602 is formed on the surface of a glasssubstrate 601 by means of sputtering. The resulting aluminum filmconstitutes the gate electrode in the later steps.

Once the aluminum film 602 is formed, a 500-Å-thick silicon nitride film603 is formed thereon by plasma CVD. Thus is obtained a structure shownin FIG. 6A.

A gate electrode 604 is formed thereafter by patterning. Silicon nitridefilm 605 remains on the gate electrode 604. The structure shown in FIG.6B is obtained in this manner.

Dense anodic oxide films 606 and 607 are each formed at a thickness of500 Å by effecting anodic oxidation using the gate electrode 604 as theanode.

Because silicon nitride film 605 still remains in this step, anodicoxide films are formed on only the side planes of the gate electrode604. Thus is obtained a structure as shown in FIG. 6C.

A 1,000-Å-thick silicon oxide film 608 which functions as a gateinsulating film is formed thereafter by means of plasma CVD. In order toform an active layer, a 500-Å-thick amorphous silicon film (not shown)is formed by plasma CVD. A crystalline silicon film (not shown) isobtained thereafter by irradiating a laser light to the amorphoussilicon film.

Once the crystalline silicon film (not shown) is obtained, patterning isperformed to form an active layer pattern comprising regions 609, 610,and 611.

Then, a resist mask 612 is formed by performing exposure from the backside of the substrate 601 while using the gate electrode 604 as a mask(see FIG. 6D).

In this state, plasma doping is performed to dope P atoms. Thus, asource region 609, a drain region 611, and a channel region 610 areformed in a self-aligned manner in the present doping step. Thus isobtained a structure shown in FIG. 6D.

Upon completion of the doping step above, laser light is irradiated tothe structure to activate the doped atoms and to anneal the dopedregions.

Then, a 2000-Å-thick silicon nitride film is formed by plasma CVD toprovide a first interlayer insulating film 616, and a polyimide film isformed thereafter to obtain a second interlayer insulating film 613. Thestructure thus obtained is shown in FIG. 7A.

After perforating contact holes, a source electrode 614 and a drainelectrode 615 are formed. Hydrogenation is performed finally to completethe transistor.

Although not shown, another contact to the gate electrode 604 is formedby perforating a contact hole on the upper portion of wiring extendedfrom the gate electrode 604 in a separate portion. Thus is obtained astructure shown in FIG. 7B.

Also in the constitution of the present example, hillock and whisker areprevented from generating as a whole because an anodic oxide film isformed on the side planes of the gate electrode 604 and because asilicon nitride film is formed on the upper plane of the gate electrode604. Moreover, because a silicon nitride film is formed on the upperplane of the gate electrode, the formation of contact holes isfacilitated.

EXAMPLE 5

The relation between the concentration of impurities in an aluminum filmcontaining 0.18% by weight of scandium and the generation of hillock isshown in this example. A 3,000-Å-thick aluminum film was formed bysputtering, and was subjected to heat treatment at 350° C. for aduration of 1 hour under gaseous hydrogen atmosphere. Table 1 shows therelation between the observed height of the hillock and theconcentration of impurities in the thus obtained film.

TABLE 1 Impurity concentration Sample in film Nos. (atoms · cm⁻³) (max.value) Maximum height of Hillock No. Oxygen Carbon Nitrogen ( Å ) 1 2 ×10²⁰ 9 × 10¹⁹ 1 × 10¹⁹ 1552 2 7 × 10¹⁹ 4 × 10¹⁹ 7 × 10¹⁸ 1627 3 7 × 10¹⁹2 × 10¹⁹ 5 × 10¹⁸ 2472 4 1 × 10¹⁹ 8 × 10¹⁸ 2 × 10¹⁸ 837 5 8 × 10¹⁸ 4 ×10¹⁸ 6 × 10¹⁷ 322 6 7 × 10¹⁸ 4 × 10¹⁸ 7 × 10¹⁷ 481 7 7 × 10¹⁸ 5 × 10¹⁸ 7× 10¹⁷ 373

Referring to Table 1, the concentration of impurities differs from asample to another. The difference arises due to factors such as thevaried duration of evacuation during sputtering, whether or not cleaningof chamber of the sputtering apparatus was performed, and howmaintenance was carried out on the evacuation pump.

The height of the hillock was determined by observation under crosssection SEM (scanning electron microscope) and AFM (atomic forcemicroscope). The concentration of impurity elements is given by themaximum value measured by using SIMS (secondary ion mass spectroscopy).

It is apparent from Table 1 that the generation of hillock can besuppressed by decreasing the concentration of oxygen (O), carbon (C),and nitrogen (N) contained in the film.

By taking into consideration the film thickness of the interlayerinsulating film and the like, hillock not greater than 500 Å in heightare allowable in view of practical use. Conclusively, Table 1 reads thatthe allowable concentration of the impurities is 7×10¹⁸ atoms·cm⁻³ orlower for oxygen, 5×10¹⁸ atoms·cm⁻³ or lower for carbon, and 7×10¹⁷atoms·cm⁻³ or lower for nitrogen.

Care should be taken in using SIMS for the measurement of the impurityconcentration, because a false value is sometimes measured in thevicinity of the interface of the film.

Explanation of the Apparatus

The apparatus for use in an embodiment of the present invention isdescribed below. FIG. 8 schematically shows the apparatus. Referring toFIG. 8, the apparatus is of a multi-chamber type in which a plurality ofprocesses are performed continuously without exposing the sample to theatmosphere. Each of the chambers is equipped with the necessaryevacuation system, and maintains the airtight environment.

Referring to FIG. 8, the apparatus comprises a substrate feeding chamber804 and a substrate discharging chamber 805. A plurality of substrates(samples) set in a cassette 815 are wholly fed into the substratefeeding chamber 804 from the outside. The substrates subjected to theprocess are set again in a cassette 816, and once process for apredetermined number of substrates are finished, the cassette 816 withsuch substrates is wholly drawn again from the chamber.

A substrate transportation chamber 801 transports a substrate 800 to adesired chamber by using a robot arm 814.

A chamber 803 is provided to form aluminum films by means of sputtering.The chamber 803 is equipped with a cryo pump to control theconcentration of impurities in the aluminum film to a predeterminedlevel or lower.

A sputtering apparatus 802 is used to form a germanium (or silver) filmto realize favorable electric contact in forming contacts. The chamber802 is also equipped with a cryo pump to prevent the incorporation ofimpurities as much as possible.

A chamber 807 is provided to perform heat treatment. In this chamber,heating is effected by irradiating a light emitted from a lamp.

A chamber 806 is further provided to form a silicon nitride film byusing plasma CVD.

Gate valves, which are gate-type sections or partitions 810, 809, 808,813, 812, and 811, are provided between the substrate transportationchamber 801 and each of the peripheral chambers for performing varioustypes of processes.

An example of operating the apparatus with reference to FIG. 8 isdescribed below. The present operation comprises sequential processes offorming an aluminum film by film deposition, forming a germanium film,heat treatment, and forming a silicon nitride film.

In the processes, the gate valves are all closed except for the onethrough which the sample is passed. First, a plurality of substrates(samples) for forming thereon an aluminum film are set inside a cassette815, and are transported into the substrate feeding chamber 804. Asubstrate is then transported into the chamber 803 by using the robotarm 814.

Upon completion of the formation of the aluminum film inside the chamber803, the substrate is transferred to the chamber 806 to form thereon asilicon nitride film. Then, the substrate is placed inside the cassette816 of the substrate discharging chamber 805 to complete the entireprocess.

In case of forming an aluminum film for use as the contact after theformation of contact holes, a germanium film is formed inside thechamber 802 after forming the aluminum film in the chamber 803, andthereafter heat treatment is carried out in the heating chamber 807 toperform reflow treatment, i.e., the annealing for forming the contact.

Reflow treatment provides a favorable electric contact between aluminumand the electrode to be brought into contact therewith (i.e., theelectrode exposed at the bottom portion of the contact hole), becausethe melting point drops at the contact portion between aluminum andgermanium, and germanium thereby diffuses into the aluminum film by theheat treatment.

EXAMPLE 6

The present example relates to a case of employing, in the place ofanodic oxidation, plasma oxidation for the formation of a metallic oxidefilm on the surface of aluminum. Plasma oxidation can be performed byeffecting high frequency discharge under a reduced-pressure oxidizingatmosphere.

EXAMPLE 7

The present invention disclosed in the present specification isapplicable to an active matrix electro-optical device. Electro-opticaldevices include, for instance, a liquid crystal display device, an EL(electro-luminescent) display device, and an EC (electro-chromic)display device.

Application examples of the commercially available products include TVcameras, personal computers, car navigation systems, TV projectionsystems, video cameras, etc. Those products are briefly described belowwith reference to FIGS. 9A to 9E.

FIG. 9A shows a TV camera comprising a main body 2001, a camera 2002, adisplay device 2003, and operation switches 2004. The display device2003 is also used as a view finder.

FIG. 9B shows a personal computer comprising a main body 2101, a cover2102, a keyboard 2103, and a display device 2104. The display device2104 is used as a monitor, and a diagonal of ten and several inches insize is required.

Referring to FIG. 9C, a car navigation system comprises a main body2301, a display device 2302, operation switches 2303, and an antenna2304. The display device 2302 is used as a monitor, but the main usagethereof is to display a map. Thus, the allowance in resolution isrelatively large.

Referring to FIG. 9D, a TV projection system comprises a main body 2401,a light source 2402, a display device 2403, mirrors 2404 and 2405, and ascreen 2406. Because the image displayed in the display device 2403 isprojected to the screen 2406, the display device 2403 must have highresolution.

Referring to FIG. 9E, a video camera comprises a main body 2501, adisplay device 2502, an eye piece 2503, operation switches 2504, and atape holder 2505. Since the real time view of the photographed image canbe seen through the eye piece 2503, a user may take pictures whileviewing the image.

As described above, by using the present invention, not only the problemconcerning the heat resistance of an aluminum wiring is overcome, butalso the problematic formation of contacts is facilitated in case ananodic oxidation film is formed.

Although aluminum is used for the gate electrode and the gate line inthe foregoing embodiments, the present invention is applicable to anodicoxidizable metals such as tantalum in place of aluminum.

While the invention has been described in detail, it should beunderstood that the present invention is not to be construed as beinglimited thereto, and that any modifications can be made withoutdeparting from the scope of claims.

1. A semiconductor device comprising: a substrate; a plurality of gatelines formed over the substrate; a plurality of source lines formed overthe substrate wherein a matrix is formed by said plurality of gate linesand said plurality of source lines; at least one thin film transistorelectrically connected to one of the gate lines and one of the sourcelines; and at least one pixel electrode electrically connected to saidat least one thin film transistor, wherein at least one of said gatelines comprises aluminum and contains oxygen atoms at a concentration of8×10¹⁸ atoms/cm³ or less, carbon atoms at a concentration of 5×10¹⁸atoms/cm³ or less, and nitrogen atoms at a concentration of 7×10¹⁷atoms/cm³ or less.
 2. A semiconductor device comprising: a substrate; atleast one thin film transistor formed over the substrate; an interlayerinsulating film formed over the thin film transistor; at least oneelectrode formed over said interlayer insulating film and electricallyconnected to source or drain of said thin film transistor through acontact hole of the insulating film wherein said at least one electrodecomprises a first film comprising titanium, a second film comprisingaluminum and a third film comprising titanium with the second film beinginterposed between the first and the third films; and at least one pixelelectrode electrically connected to said at least one electrode, whereina gate electrode of said thin film transistor comprises aluminum andcontains oxygen atoms at a concentration of 8×10¹⁸ atoms/cm³ or less,carbon atoms at a concentration of 5×10¹⁸ atoms/cm³ or less, andnitrogen atoms at a concentration of 7×10¹⁷ atoms/cm³ or less.
 3. Asemiconductor device comprising: a substrate; a plurality of gate linesformed over the substrate; a plurality of source lines formed over thesubstrate wherein a matrix is formed by said plurality of gate lines andsaid plurality of source lines; at least one thin film transistorelectrically connected to one of the gate lines and one of the sourcelines; and at least one pixel electrode electrically connected to saidat least one thin film transistor, wherein at least one of said sourcelines comprises aluminum and contains oxygen atoms at a concentration of8×10¹⁸ atoms/cm³ or less, carbon atoms at a concentration of 5×10¹⁸atoms/cm³ or less, and nitrogen atoms at a concentration of 7×10¹⁷atoms/cm³ or less.
 4. A semiconductor device comprising: a substrate; atleast one thin film transistor formed over the substrate; an interlayerinsulating film formed over the thin film transistor; at least oneelectrode formed over said interlayer insulating film and electricallyconnected to source or drain of said thin film transistor through acontact hole of the insulating film wherein said at least one electrodecomprises a pair of titanium films and an aluminum film interposedtherebetween; and at least one pixel electrode electrically connected tosaid at least one electrode, wherein said aluminum film contains oxygenatoms at a concentration of 8×10¹⁸ atoms/cm³ or less, carbon atoms at aconcentration of 5×10¹⁸ atoms/cm³ or less, and nitrogen atoms at aconcentration of 7×10¹⁷ atoms/cm³ or less.
 5. A semiconductor devicecomprising: a substrate; a gate electrode comprising an aluminum layer;a gate insulating film formed over the gate electrode; and asemiconductor film having at least a channel region located over thegate electrode with the gate insulating film interposed therebetween,wherein said aluminum layer contains oxygen atoms at a concentration of8×10¹⁸ atoms/cm³ or less, carbon atoms at a concentration of 5×10¹⁸atoms/cm³ or less, and nitrogen atoms at a concentration of 7×10¹⁷atoms/cm³ or less.
 6. A semiconductor device comprising: a substrate; agate electrode comprising an aluminum layer; a first insulating layercomprising silicon nitride formed over the gate electrode; a secondinsulating layer formed over the first insulating layer; a semiconductorfilm having at least a channel region located over the gate electrodewith the first and second insulating layers interposed therebetween,wherein said aluminum layer contains oxygen atoms at a concentration of8×10¹⁸ atoms/cm³ or less, carbon atoms at a concentration of 5×10¹⁸atoms/cm³ or less, and nitrogen atoms at a concentration of 7×10¹⁷atoms/cm³ or less.
 7. A personal computer comprising: a substrate; aplurality of gate lines formed over the substrate; a plurality of sourcelines formed over the substrate wherein a matrix is formed by saidplurality of gate lines and said plurality of source lines; at least onethin film transistor electrically connected to one of the gate lines andone of the source lines; and at least one pixel electrode electricallyconnected to said at least one thin film transistor, wherein at leastone of said gate lines comprises aluminum and contains oxygen atoms at aconcentration of 8×10¹⁸ atoms/cm³ or less, carbon atoms at aconcentration of 5×10¹⁸ atoms/cm³ or less, and nitrogen atoms at aconcentration of 7×10¹⁷ atoms/cm³ or less.
 8. A personal computercomprising: a substrate; at least one thin film transistor formed overthe substrate; an interlayer insulating film formed over the thin filmtransistor; at least one electrode formed over said interlayerinsulating film and electrically connected to source or drain of saidthin film transistor through a contact hole of the insulating filmwherein said at least one electrode comprises a first film comprisingtitanium, a second film comprising aluminum and a third film comprisingtitanium with the second film being interposed between the first and thesecond films; and at least one pixel electrode electrically connected tosaid at least one electrode, wherein a gate electrode of said thin filmtransistor comprises aluminum and contains oxygen atoms at aconcentration of 8×10¹⁸ atoms/cm³ or less, carbon atoms at aconcentration of 5×10¹⁸ atoms/cm³ or less, and nitrogen atoms at aconcentration of 7×10¹⁷ atoms/cm³ or less.
 9. A personal computercomprising: a substrate; a plurality of gate lines formed over thesubstrate; a plurality of source lines formed over the substrate whereina matrix is formed by said plurality of gate lines and said plurality ofsource lines; at least one thin film transistor electrically connectedto one of the gate lines and one of the source lines; and at least onepixel electrode electrically connected to said at least one thin filmtransistor, wherein at least one of said source lines comprises aluminumand contains oxygen atoms at a concentration of 8×10¹⁸ atoms/cm³ orless, carbon atoms at a concentration of 5×10¹⁸ atoms/cm³ or less, andnitrogen atoms at a concentration of 7×10¹⁷ atoms/cm³ or less.
 10. Apersonal computer comprising: a substrate; at least one thin filmtransistor formed over the substrate; an interlayer insulating filmformed over the thin film transistor; at least one electrode formed oversaid interlayer insulating film and electrically connected to source ordrain of said thin film transistor through a contact hole of theinsulating film wherein said at least one electrode comprises a pair oftitanium films and an aluminum film interposed therebetween; and atleast one pixel electrode electrically connected to said at least oneelectrode, wherein said aluminum film contains oxygen atoms at aconcentration of 8×10¹⁸ atoms/cm³ or less, carbon atoms at aconcentration of 5×10¹⁸ atoms/cm³ or less, and nitrogen atoms at aconcentration of 7×10¹⁷ atoms/cm³ or less.
 11. A personal computercomprising: a substrate; a gate electrode comprising an aluminum layer;a gate insulating film formed over the gate electrode; and asemiconductor film having at least a channel region located over thegate electrode with the gate insulating film interposed therebetween,wherein said aluminum layer contains oxygen atoms at a concentration of8×10¹⁸ atoms/cm³ or less, carbon atoms at a concentration of 5×10¹⁸atoms/cm³ or less, and nitrogen atoms at a concentration of 7×10¹⁷atoms/cm³ or less.
 12. A personal computer comprising: a substrate; agate electrode comprising an aluminum layer; a first insulating layercomprising silicon nitride formed over the gate electrode; a secondinsulating layer formed over the first insulating layer; a semiconductorfilm having at least a channel region located over the gate electrodewith the first and second insulating layers interposed therebetween,wherein said aluminum layer contains oxygen atoms at a concentration of8×10¹⁸ atoms/cm³ or less, carbon atoms at a concentration of 5×10¹⁸atoms/cm³ or less, and nitrogen atoms at a concentration of 7×10¹⁷atoms/cm³ or less.